Shuttle valves may be employed in connection with underwater oil field equipment. For example, the lower ends of two hydraulic fluid accumulators (e.g., tanks with air space in the top thereof) may be connected to the inlets of a shuttle valve. Each of two high pressure flow lines feeding the accumulators may be connected thereto between the shuttle valve and one of the tanks, via ancillary control valves. The outlet of the shuttle valve will supply fluid to the valve outlet from whichever one of inlets is connected to the flow line having the higher pressure.
It is especially important that underwater shuttle valves have a long trouble-free life because of their inaccessibility. Due to the high working pressures, the possible differential pressure on such shuttle valves is very high. As a result, when the pressure differential on the opposite sides of the shuttle of the valve is high, the valve may move at a high velocity. Sometimes the resulting high velocity of a shuttle as it moves from one seat to another creates a sufficient energy impact with the valve cage to cause the shuttle to be damaged, or the resilient seal of the valve to be extruded, thus disrupting proper valve operation. There is a need therefore for a shuttle valve having a shuttle assembly that will operate reliably for extended periods of time.